The present disclosure relates to a circulating dry scrubber (CDS) structure. This structure is used to remove particulates and other contaminants from flue gas produced during combustion, and is part of a dry scrubber flue gas desulfurization (FGD) system. In particular, sulfur dioxide (SO2), sulfur trioxide (SO3), HCl, and other acid gases can be captured. The structure permits the related components to be removed or to be placed at an elevation closer to grade. This, among other things, improves material usage and reduces capital costs and operating costs, and improves capture of particulates and/or other contaminants.
During combustion, the chemical energy in a fuel is converted to thermal heat, which can be used in various forms for different applications. The fuels used in the combustion process can include a wide range of solid, liquid, and gaseous substances, including coal, oil (diesel, No. 2, Bunker C or No. 6), natural gas, wood, tires, biomass, etc.
Combustion transforms the fuel into a large number of chemical compounds. Water (H2O) and carbon dioxide (CO2) are the primary products of complete combustion. However, other combustion reactions with chemical components in the fuel result in undesirable byproducts. Depending on the fuel used, such byproducts may include particulates (e.g. fly ash), acid gases such as sulfur oxides (SOX) or nitric oxides (NOx), metals such as mercury or arsenic, carbon monoxide (CO), and hydrocarbons (HC). The emissions levels of many of these byproducts are regulated by governmental entities, such as the U.S. Environmental Protection Agency (EPA).
Several different technologies exist for removing such byproducts from the flue gas. In one method, known as spray drying chemical absorption or dry scrubbing, an aqueous alkaline solution or slurry, which has been finely atomized, is sprayed into the hot flue gas downstream of the combustion chamber in which the fuel was combusted. The alkaline reagent reacts with the pollutants, and particulates are formed. The water evaporates and cools the hot flue gas. The exiting cleaned flue gas typically has a moisture content of about 10% to about 15%. The flue gas then travels to a particulate collection device, generally a baghouse, where the particulates are removed from the flue gas, which is then sent to a stack.
The layout of a circulating dry scrubber (CDS) flue gas desulfurization (FGD) system generally results in many different components being elevated a great distance above grade. The number of components and the structural steel needed to elevate the components add significant capital costs and operating costs to the overall system. It would be desirable to provide alternative CDS-FGD systems that can reduce such costs as well as improve or maintain combustion byproduct removal.